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Abstract Detail

Systematics Section/ASPT

Samarakoon, Tharangamala [1], Alford, Mac [2].

Historical Biogeography of Samydaceae.

Samydaceae are a family of 14 genera and about 240 species. Most of the genera are restricted geographically to the Americas, Africa, or southeast Asia. One genus, Casearia, has a wide pantropical distribution in all former Gondwana landmasses, including Africa, Madagascar, Australia, India, Sri Lanka, the Malay Archipelago, and South America. Several biogeographers have hypothesized that similar distributions are the result of ancient Gondwana vicariance. Recent biogeographical studies in the related Malpighiaceae favors the “American colonist” hypothesis, in which Malpighiaceae originated in northern South America, in isolation from Africa, and dispersed eastward across the Atlantic at least twice. This hypothesis predicts that the ages of Malpighiaceae and of divergences between New World and Old World lineages are younger than the last known land connection between South America and Africa, in contrast to the classic “Gondwanian aborigine” hypothesis, which argues that the diversity of Malpighiaceae originated before western Gondwana divided about 105 million years ago (Ma). In this study we took advantage of the distribution of Casearia, a genus with high species richness in both the neotropics and paleotropics and across the major land masses, to infer the ancestral area for the whole family. Divergence times in the family were estimated by analyzing the sequences of four DNA regions (plastid trnL intron, trnL-F spacer, and ndhF; nuclear GBSSI) from 64 taxa and 4 outgroup taxa, using Bayesian molecular dating analysis (BEAST). Two fossil calibration points and age constraints for the family were applied. Estimates of molecular divergence time and ancestral ranges for Samydaceae indicate that the family originated in South America in the Eocene with at least two main migration events from the Americas to the Old World during the late Oligocene.

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1 - University Of Southern Mississippi, Department Of Biological Sciences, Alford Lab, 118 College Drive #5018, Hattiesburg, MS, 39406, USA
2 - University Of Southern Mississippi, Department Of Biological Sciences, 118 COLLEGE DRIVE #5018, HATTIESBURG, MS, 39406-0001, USA

Gondwanan vicariance
molecular clock.

Presentation Type: Oral Paper:Papers for Sections
Session: 30
Location: Payette/Boise Centre
Date: Tuesday, July 29th, 2014
Time: 2:45 PM
Number: 30006
Abstract ID:865
Candidate for Awards:George R. Cooley Award


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